// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#if V8_TARGET_ARCH_X64

#include "src/regexp/x64/regexp-macro-assembler-x64.h"

#include "src/heap/factory.h"
#include "src/log.h"
#include "src/macro-assembler.h"
#include "src/objects-inl.h"
#include "src/regexp/regexp-macro-assembler.h"
#include "src/regexp/regexp-stack.h"
#include "src/unicode.h"

namespace v8 {
namespace internal {

    /*
 * This assembler uses the following register assignment convention
 * - rdx : Currently loaded character(s) as Latin1 or UC16.  Must be loaded
 *         using LoadCurrentCharacter before using any of the dispatch methods.
 *         Temporarily stores the index of capture start after a matching pass
 *         for a global regexp.
 * - rdi : Current position in input, as negative offset from end of string.
 *         Please notice that this is the byte offset, not the character
 *         offset!  Is always a 32-bit signed (negative) offset, but must be
 *         maintained sign-extended to 64 bits, since it is used as index.
 * - rsi : End of input (points to byte after last character in input),
 *         so that rsi+rdi points to the current character.
 * - rbp : Frame pointer.  Used to access arguments, local variables and
 *         RegExp registers.
 * - rsp : Points to tip of C stack.
 * - rcx : Points to tip of backtrack stack.  The backtrack stack contains
 *         only 32-bit values.  Most are offsets from some base (e.g., character
 *         positions from end of string or code location from Code pointer).
 * - r8  : Code object pointer.  Used to convert between absolute and
 *         code-object-relative addresses.
 *
 * The registers rax, rbx, r9 and r11 are free to use for computations.
 * If changed to use r12+, they should be saved as callee-save registers.
 * The macro assembler special register r13 (kRootRegister) isn't special
 * during execution of RegExp code (it doesn't hold the value assumed when
 * creating JS code), so Root related macro operations can be used.
 *
 * Each call to a C++ method should retain these registers.
 *
 * The stack will have the following content, in some order, indexable from the
 * frame pointer (see, e.g., kStackHighEnd):
 *    - Isolate* isolate     (address of the current isolate)
 *    - direct_call          (if 1, direct call from JavaScript code, if 0 call
 *                            through the runtime system)
 *    - stack_area_base      (high end of the memory area to use as
 *                            backtracking stack)
 *    - capture array size   (may fit multiple sets of matches)
 *    - int* capture_array   (int[num_saved_registers_], for output).
 *    - end of input         (address of end of string)
 *    - start of input       (address of first character in string)
 *    - start index          (character index of start)
 *    - String input_string  (input string)
 *    - return address
 *    - backup of callee save registers (rbx, possibly rsi and rdi).
 *    - success counter      (only useful for global regexp to count matches)
 *    - Offset of location before start of input (effectively character
 *      string start - 1).  Used to initialize capture registers to a
 *      non-position.
 *    - At start of string (if 1, we are starting at the start of the
 *      string, otherwise 0)
 *    - register 0  rbp[-n]   (Only positions must be stored in the first
 *    - register 1  rbp[-n-8]  num_saved_registers_ registers)
 *    - ...
 *
 * The first num_saved_registers_ registers are initialized to point to
 * "character -1" in the string (i.e., char_size() bytes before the first
 * character of the string).  The remaining registers starts out uninitialized.
 *
 * The first seven values must be provided by the calling code by
 * calling the code's entry address cast to a function pointer with the
 * following signature:
 * int (*match)(String input_string,
 *              int start_index,
 *              Address start,
 *              Address end,
 *              int* capture_output_array,
 *              int num_capture_registers,
 *              byte* stack_area_base,
 *              bool direct_call = false,
 *              Isolate* isolate);
 */

#define __ ACCESS_MASM((&masm_))

    const int RegExpMacroAssemblerX64::kRegExpCodeSize;

    RegExpMacroAssemblerX64::RegExpMacroAssemblerX64(Isolate* isolate, Zone* zone,
        Mode mode,
        int registers_to_save)
        : NativeRegExpMacroAssembler(isolate, zone)
        , masm_(isolate, CodeObjectRequired::kYes,
              NewAssemblerBuffer(kRegExpCodeSize))
        , no_root_array_scope_(&masm_)
        , code_relative_fixup_positions_(zone)
        , mode_(mode)
        , num_registers_(registers_to_save)
        , num_saved_registers_(registers_to_save)
        , entry_label_()
        , start_label_()
        , success_label_()
        , backtrack_label_()
        , exit_label_()
    {
        DCHECK_EQ(0, registers_to_save % 2);
        __ jmp(&entry_label_); // We'll write the entry code when we know more.
        __ bind(&start_label_); // And then continue from here.
    }

    RegExpMacroAssemblerX64::~RegExpMacroAssemblerX64()
    {
        // Unuse labels in case we throw away the assembler without calling GetCode.
        entry_label_.Unuse();
        start_label_.Unuse();
        success_label_.Unuse();
        backtrack_label_.Unuse();
        exit_label_.Unuse();
        check_preempt_label_.Unuse();
        stack_overflow_label_.Unuse();
    }

    int RegExpMacroAssemblerX64::stack_limit_slack()
    {
        return RegExpStack::kStackLimitSlack;
    }

    void RegExpMacroAssemblerX64::AdvanceCurrentPosition(int by)
    {
        if (by != 0) {
            __ addq(rdi, Immediate(by * char_size()));
        }
    }

    void RegExpMacroAssemblerX64::AdvanceRegister(int reg, int by)
    {
        DCHECK_LE(0, reg);
        DCHECK_GT(num_registers_, reg);
        if (by != 0) {
            __ addq(register_location(reg), Immediate(by));
        }
    }

    void RegExpMacroAssemblerX64::Backtrack()
    {
        CheckPreemption();
        // Pop Code offset from backtrack stack, add Code and jump to location.
        Pop(rbx);
        __ addq(rbx, code_object_pointer());
        __ jmp(rbx);
    }

    void RegExpMacroAssemblerX64::Bind(Label* label)
    {
        __ bind(label);
    }

    void RegExpMacroAssemblerX64::CheckCharacter(uint32_t c, Label* on_equal)
    {
        __ cmpl(current_character(), Immediate(c));
        BranchOrBacktrack(equal, on_equal);
    }

    void RegExpMacroAssemblerX64::CheckCharacterGT(uc16 limit, Label* on_greater)
    {
        __ cmpl(current_character(), Immediate(limit));
        BranchOrBacktrack(greater, on_greater);
    }

    void RegExpMacroAssemblerX64::CheckAtStart(Label* on_at_start)
    {
        __ leaq(rax, Operand(rdi, -char_size()));
        __ cmpq(rax, Operand(rbp, kStringStartMinusOne));
        BranchOrBacktrack(equal, on_at_start);
    }

    void RegExpMacroAssemblerX64::CheckNotAtStart(int cp_offset,
        Label* on_not_at_start)
    {
        __ leaq(rax, Operand(rdi, -char_size() + cp_offset * char_size()));
        __ cmpq(rax, Operand(rbp, kStringStartMinusOne));
        BranchOrBacktrack(not_equal, on_not_at_start);
    }

    void RegExpMacroAssemblerX64::CheckCharacterLT(uc16 limit, Label* on_less)
    {
        __ cmpl(current_character(), Immediate(limit));
        BranchOrBacktrack(less, on_less);
    }

    void RegExpMacroAssemblerX64::CheckGreedyLoop(Label* on_equal)
    {
        Label fallthrough;
        __ cmpl(rdi, Operand(backtrack_stackpointer(), 0));
        __ j(not_equal, &fallthrough);
        Drop();
        BranchOrBacktrack(no_condition, on_equal);
        __ bind(&fallthrough);
    }

    void RegExpMacroAssemblerX64::CheckNotBackReferenceIgnoreCase(
        int start_reg, bool read_backward, bool unicode, Label* on_no_match)
    {
        Label fallthrough;
        ReadPositionFromRegister(rdx, start_reg); // Offset of start of capture
        ReadPositionFromRegister(rbx, start_reg + 1); // Offset of end of capture
        __ subq(rbx, rdx); // Length of capture.

        // -----------------------
        // rdx  = Start offset of capture.
        // rbx = Length of capture

        // At this point, the capture registers are either both set or both cleared.
        // If the capture length is zero, then the capture is either empty or cleared.
        // Fall through in both cases.
        __ j(equal, &fallthrough);

        // -----------------------
        // rdx - Start of capture
        // rbx - length of capture
        // Check that there are sufficient characters left in the input.
        if (read_backward) {
            __ movl(rax, Operand(rbp, kStringStartMinusOne));
            __ addl(rax, rbx);
            __ cmpl(rdi, rax);
            BranchOrBacktrack(less_equal, on_no_match);
        } else {
            __ movl(rax, rdi);
            __ addl(rax, rbx);
            BranchOrBacktrack(greater, on_no_match);
        }

        if (mode_ == LATIN1) {
            Label loop_increment;
            if (on_no_match == nullptr) {
                on_no_match = &backtrack_label_;
            }

            __ leaq(r9, Operand(rsi, rdx, times_1, 0));
            __ leaq(r11, Operand(rsi, rdi, times_1, 0));
            if (read_backward) {
                __ subq(r11, rbx); // Offset by length when matching backwards.
            }
            __ addq(rbx, r9); // End of capture
            // ---------------------
            // r11 - current input character address
            // r9 - current capture character address
            // rbx - end of capture

            Label loop;
            __ bind(&loop);
            __ movzxbl(rdx, Operand(r9, 0));
            __ movzxbl(rax, Operand(r11, 0));
            // al - input character
            // dl - capture character
            __ cmpb(rax, rdx);
            __ j(equal, &loop_increment);

            // Mismatch, try case-insensitive match (converting letters to lower-case).
            // I.e., if or-ing with 0x20 makes values equal and in range 'a'-'z', it's
            // a match.
            __ orq(rax, Immediate(0x20)); // Convert match character to lower-case.
            __ orq(rdx, Immediate(0x20)); // Convert capture character to lower-case.
            __ cmpb(rax, rdx);
            __ j(not_equal, on_no_match); // Definitely not equal.
            __ subb(rax, Immediate('a'));
            __ cmpb(rax, Immediate('z' - 'a'));
            __ j(below_equal, &loop_increment); // In range 'a'-'z'.
            // Latin-1: Check for values in range [224,254] but not 247.
            __ subb(rax, Immediate(224 - 'a'));
            __ cmpb(rax, Immediate(254 - 224));
            __ j(above, on_no_match); // Weren't Latin-1 letters.
            __ cmpb(rax, Immediate(247 - 224)); // Check for 247.
            __ j(equal, on_no_match);
            __ bind(&loop_increment);
            // Increment pointers into match and capture strings.
            __ addq(r11, Immediate(1));
            __ addq(r9, Immediate(1));
            // Compare to end of capture, and loop if not done.
            __ cmpq(r9, rbx);
            __ j(below, &loop);

            // Compute new value of character position after the matched part.
            __ movq(rdi, r11);
            __ subq(rdi, rsi);
            if (read_backward) {
                // Subtract match length if we matched backward.
                __ addq(rdi, register_location(start_reg));
                __ subq(rdi, register_location(start_reg + 1));
            }
        } else {
            DCHECK(mode_ == UC16);
            // Save important/volatile registers before calling C function.
#ifndef _WIN64
            // Caller save on Linux and callee save in Windows.
            __ pushq(rsi);
            __ pushq(rdi);
#endif
            __ pushq(backtrack_stackpointer());

            static const int num_arguments = 4;
            __ PrepareCallCFunction(num_arguments);

            // Put arguments into parameter registers. Parameters are
            //   Address byte_offset1 - Address captured substring's start.
            //   Address byte_offset2 - Address of current character position.
            //   size_t byte_length - length of capture in bytes(!)
//   Isolate* isolate or 0 if unicode flag.
#ifdef _WIN64
            DCHECK(rcx == arg_reg_1);
            DCHECK(rdx == arg_reg_2);
            // Compute and set byte_offset1 (start of capture).
            __ leaq(rcx, Operand(rsi, rdx, times_1, 0));
            // Set byte_offset2.
            __ leaq(rdx, Operand(rsi, rdi, times_1, 0));
            if (read_backward) {
                __ subq(rdx, rbx);
            }
#else // AMD64 calling convention
            DCHECK(rdi == arg_reg_1);
            DCHECK(rsi == arg_reg_2);
            // Compute byte_offset2 (current position = rsi+rdi).
            __ leaq(rax, Operand(rsi, rdi, times_1, 0));
            // Compute and set byte_offset1 (start of capture).
            __ leaq(rdi, Operand(rsi, rdx, times_1, 0));
            // Set byte_offset2.
            __ movq(rsi, rax);
            if (read_backward) {
                __ subq(rsi, rbx);
            }
#endif // _WIN64

            // Set byte_length.
            __ movq(arg_reg_3, rbx);
            // Isolate.
#ifdef V8_INTL_SUPPORT
            if (unicode) {
                __ movq(arg_reg_4, Immediate(0));
            } else // NOLINT
#endif // V8_INTL_SUPPORT
            {
                __ LoadAddress(arg_reg_4, ExternalReference::isolate_address(isolate()));
            }

            { // NOLINT: Can't find a way to open this scope without confusing the
                // linter.
                AllowExternalCallThatCantCauseGC scope(&masm_);
                ExternalReference compare = ExternalReference::re_case_insensitive_compare_uc16(isolate());
                __ CallCFunction(compare, num_arguments);
            }

            // Restore original values before reacting on result value.
            __ Move(code_object_pointer(), masm_.CodeObject());
            __ popq(backtrack_stackpointer());
#ifndef _WIN64
            __ popq(rdi);
            __ popq(rsi);
#endif

            // Check if function returned non-zero for success or zero for failure.
            __ testq(rax, rax);
            BranchOrBacktrack(zero, on_no_match);
            // On success, advance position by length of capture.
            // Requires that rbx is callee save (true for both Win64 and AMD64 ABIs).
            if (read_backward) {
                __ subq(rdi, rbx);
            } else {
                __ addq(rdi, rbx);
            }
        }
        __ bind(&fallthrough);
    }

    void RegExpMacroAssemblerX64::CheckNotBackReference(int start_reg,
        bool read_backward,
        Label* on_no_match)
    {
        Label fallthrough;

        // Find length of back-referenced capture.
        ReadPositionFromRegister(rdx, start_reg); // Offset of start of capture
        ReadPositionFromRegister(rax, start_reg + 1); // Offset of end of capture
        __ subq(rax, rdx); // Length to check.

        // At this point, the capture registers are either both set or both cleared.
        // If the capture length is zero, then the capture is either empty or cleared.
        // Fall through in both cases.
        __ j(equal, &fallthrough);

        // -----------------------
        // rdx - Start of capture
        // rax - length of capture
        // Check that there are sufficient characters left in the input.
        if (read_backward) {
            __ movl(rbx, Operand(rbp, kStringStartMinusOne));
            __ addl(rbx, rax);
            __ cmpl(rdi, rbx);
            BranchOrBacktrack(less_equal, on_no_match);
        } else {
            __ movl(rbx, rdi);
            __ addl(rbx, rax);
            BranchOrBacktrack(greater, on_no_match);
        }

        // Compute pointers to match string and capture string
        __ leaq(rbx, Operand(rsi, rdi, times_1, 0)); // Start of match.
        if (read_backward) {
            __ subq(rbx, rax); // Offset by length when matching backwards.
        }
        __ addq(rdx, rsi); // Start of capture.
        __ leaq(r9, Operand(rdx, rax, times_1, 0)); // End of capture

        // -----------------------
        // rbx - current capture character address.
        // rbx - current input character address .
        // r9 - end of input to match (capture length after rbx).

        Label loop;
        __ bind(&loop);
        if (mode_ == LATIN1) {
            __ movzxbl(rax, Operand(rdx, 0));
            __ cmpb(rax, Operand(rbx, 0));
        } else {
            DCHECK(mode_ == UC16);
            __ movzxwl(rax, Operand(rdx, 0));
            __ cmpw(rax, Operand(rbx, 0));
        }
        BranchOrBacktrack(not_equal, on_no_match);
        // Increment pointers into capture and match string.
        __ addq(rbx, Immediate(char_size()));
        __ addq(rdx, Immediate(char_size()));
        // Check if we have reached end of match area.
        __ cmpq(rdx, r9);
        __ j(below, &loop);

        // Success.
        // Set current character position to position after match.
        __ movq(rdi, rbx);
        __ subq(rdi, rsi);
        if (read_backward) {
            // Subtract match length if we matched backward.
            __ addq(rdi, register_location(start_reg));
            __ subq(rdi, register_location(start_reg + 1));
        }

        __ bind(&fallthrough);
    }

    void RegExpMacroAssemblerX64::CheckNotCharacter(uint32_t c,
        Label* on_not_equal)
    {
        __ cmpl(current_character(), Immediate(c));
        BranchOrBacktrack(not_equal, on_not_equal);
    }

    void RegExpMacroAssemblerX64::CheckCharacterAfterAnd(uint32_t c,
        uint32_t mask,
        Label* on_equal)
    {
        if (c == 0) {
            __ testl(current_character(), Immediate(mask));
        } else {
            __ movl(rax, Immediate(mask));
            __ andq(rax, current_character());
            __ cmpl(rax, Immediate(c));
        }
        BranchOrBacktrack(equal, on_equal);
    }

    void RegExpMacroAssemblerX64::CheckNotCharacterAfterAnd(uint32_t c,
        uint32_t mask,
        Label* on_not_equal)
    {
        if (c == 0) {
            __ testl(current_character(), Immediate(mask));
        } else {
            __ movl(rax, Immediate(mask));
            __ andq(rax, current_character());
            __ cmpl(rax, Immediate(c));
        }
        BranchOrBacktrack(not_equal, on_not_equal);
    }

    void RegExpMacroAssemblerX64::CheckNotCharacterAfterMinusAnd(
        uc16 c,
        uc16 minus,
        uc16 mask,
        Label* on_not_equal)
    {
        DCHECK_GT(String::kMaxUtf16CodeUnit, minus);
        __ leal(rax, Operand(current_character(), -minus));
        __ andl(rax, Immediate(mask));
        __ cmpl(rax, Immediate(c));
        BranchOrBacktrack(not_equal, on_not_equal);
    }

    void RegExpMacroAssemblerX64::CheckCharacterInRange(
        uc16 from,
        uc16 to,
        Label* on_in_range)
    {
        __ leal(rax, Operand(current_character(), -from));
        __ cmpl(rax, Immediate(to - from));
        BranchOrBacktrack(below_equal, on_in_range);
    }

    void RegExpMacroAssemblerX64::CheckCharacterNotInRange(
        uc16 from,
        uc16 to,
        Label* on_not_in_range)
    {
        __ leal(rax, Operand(current_character(), -from));
        __ cmpl(rax, Immediate(to - from));
        BranchOrBacktrack(above, on_not_in_range);
    }

    void RegExpMacroAssemblerX64::CheckBitInTable(
        Handle<ByteArray> table,
        Label* on_bit_set)
    {
        __ Move(rax, table);
        Register index = current_character();
        if (mode_ != LATIN1 || kTableMask != String::kMaxOneByteCharCode) {
            __ movq(rbx, current_character());
            __ andq(rbx, Immediate(kTableMask));
            index = rbx;
        }
        __ cmpb(FieldOperand(rax, index, times_1, ByteArray::kHeaderSize),
            Immediate(0));
        BranchOrBacktrack(not_equal, on_bit_set);
    }

    bool RegExpMacroAssemblerX64::CheckSpecialCharacterClass(uc16 type,
        Label* on_no_match)
    {
        // Range checks (c in min..max) are generally implemented by an unsigned
        // (c - min) <= (max - min) check, using the sequence:
        //   leal(rax, Operand(current_character(), -min)) or sub(rax, Immediate(min))
        //   cmpl(rax, Immediate(max - min))
        switch (type) {
        case 's':
            // Match space-characters
            if (mode_ == LATIN1) {
                // One byte space characters are '\t'..'\r', ' ' and \u00a0.
                Label success;
                __ cmpl(current_character(), Immediate(' '));
                __ j(equal, &success, Label::kNear);
                // Check range 0x09..0x0D
                __ leal(rax, Operand(current_character(), -'\t'));
                __ cmpl(rax, Immediate('\r' - '\t'));
                __ j(below_equal, &success, Label::kNear);
                // \u00a0 (NBSP).
                __ cmpl(rax, Immediate(0x00A0 - '\t'));
                BranchOrBacktrack(not_equal, on_no_match);
                __ bind(&success);
                return true;
            }
            return false;
        case 'S':
            // The emitted code for generic character classes is good enough.
            return false;
        case 'd':
            // Match ASCII digits ('0'..'9')
            __ leal(rax, Operand(current_character(), -'0'));
            __ cmpl(rax, Immediate('9' - '0'));
            BranchOrBacktrack(above, on_no_match);
            return true;
        case 'D':
            // Match non ASCII-digits
            __ leal(rax, Operand(current_character(), -'0'));
            __ cmpl(rax, Immediate('9' - '0'));
            BranchOrBacktrack(below_equal, on_no_match);
            return true;
        case '.': {
            // Match non-newlines (not 0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
            __ movl(rax, current_character());
            __ xorl(rax, Immediate(0x01));
            // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
            __ subl(rax, Immediate(0x0B));
            __ cmpl(rax, Immediate(0x0C - 0x0B));
            BranchOrBacktrack(below_equal, on_no_match);
            if (mode_ == UC16) {
                // Compare original value to 0x2028 and 0x2029, using the already
                // computed (current_char ^ 0x01 - 0x0B). I.e., check for
                // 0x201D (0x2028 - 0x0B) or 0x201E.
                __ subl(rax, Immediate(0x2028 - 0x0B));
                __ cmpl(rax, Immediate(0x2029 - 0x2028));
                BranchOrBacktrack(below_equal, on_no_match);
            }
            return true;
        }
        case 'n': {
            // Match newlines (0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
            __ movl(rax, current_character());
            __ xorl(rax, Immediate(0x01));
            // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
            __ subl(rax, Immediate(0x0B));
            __ cmpl(rax, Immediate(0x0C - 0x0B));
            if (mode_ == LATIN1) {
                BranchOrBacktrack(above, on_no_match);
            } else {
                Label done;
                BranchOrBacktrack(below_equal, &done);
                // Compare original value to 0x2028 and 0x2029, using the already
                // computed (current_char ^ 0x01 - 0x0B). I.e., check for
                // 0x201D (0x2028 - 0x0B) or 0x201E.
                __ subl(rax, Immediate(0x2028 - 0x0B));
                __ cmpl(rax, Immediate(0x2029 - 0x2028));
                BranchOrBacktrack(above, on_no_match);
                __ bind(&done);
            }
            return true;
        }
        case 'w': {
            if (mode_ != LATIN1) {
                // Table is 256 entries, so all Latin1 characters can be tested.
                __ cmpl(current_character(), Immediate('z'));
                BranchOrBacktrack(above, on_no_match);
            }
            __ Move(rbx, ExternalReference::re_word_character_map(isolate()));
            DCHECK_EQ(0, word_character_map[0]); // Character '\0' is not a word char.
            __ testb(Operand(rbx, current_character(), times_1, 0),
                current_character());
            BranchOrBacktrack(zero, on_no_match);
            return true;
        }
        case 'W': {
            Label done;
            if (mode_ != LATIN1) {
                // Table is 256 entries, so all Latin1 characters can be tested.
                __ cmpl(current_character(), Immediate('z'));
                __ j(above, &done);
            }
            __ Move(rbx, ExternalReference::re_word_character_map(isolate()));
            DCHECK_EQ(0, word_character_map[0]); // Character '\0' is not a word char.
            __ testb(Operand(rbx, current_character(), times_1, 0),
                current_character());
            BranchOrBacktrack(not_zero, on_no_match);
            if (mode_ != LATIN1) {
                __ bind(&done);
            }
            return true;
        }

        case '*':
            // Match any character.
            return true;
        // No custom implementation (yet): s(UC16), S(UC16).
        default:
            return false;
        }
    }

    void RegExpMacroAssemblerX64::Fail()
    {
        STATIC_ASSERT(FAILURE == 0); // Return value for failure is zero.
        if (!global()) {
            __ Set(rax, FAILURE);
        }
        __ jmp(&exit_label_);
    }

    Handle<HeapObject> RegExpMacroAssemblerX64::GetCode(Handle<String> source)
    {
        Label return_rax;
        // Finalize code - write the entry point code now we know how many
        // registers we need.
        // Entry code:
        __ bind(&entry_label_);

        // Tell the system that we have a stack frame.  Because the type is MANUAL, no
        // is generated.
        FrameScope scope(&masm_, StackFrame::MANUAL);

        // Actually emit code to start a new stack frame.
        __ pushq(rbp);
        __ movq(rbp, rsp);
        // Save parameters and callee-save registers. Order here should correspond
        //  to order of kBackup_ebx etc.
#ifdef _WIN64
        // MSVC passes arguments in rcx, rdx, r8, r9, with backing stack slots.
        // Store register parameters in pre-allocated stack slots,
        __ movq(Operand(rbp, kInputString), rcx);
        __ movq(Operand(rbp, kStartIndex), rdx); // Passed as int32 in edx.
        __ movq(Operand(rbp, kInputStart), r8);
        __ movq(Operand(rbp, kInputEnd), r9);
        // Callee-save on Win64.
        __ pushq(rsi);
        __ pushq(rdi);
        __ pushq(rbx);
#else
        // GCC passes arguments in rdi, rsi, rdx, rcx, r8, r9 (and then on stack).
        // Push register parameters on stack for reference.
        DCHECK_EQ(kInputString, -1 * kSystemPointerSize);
        DCHECK_EQ(kStartIndex, -2 * kSystemPointerSize);
        DCHECK_EQ(kInputStart, -3 * kSystemPointerSize);
        DCHECK_EQ(kInputEnd, -4 * kSystemPointerSize);
        DCHECK_EQ(kRegisterOutput, -5 * kSystemPointerSize);
        DCHECK_EQ(kNumOutputRegisters, -6 * kSystemPointerSize);
        __ pushq(rdi);
        __ pushq(rsi);
        __ pushq(rdx);
        __ pushq(rcx);
        __ pushq(r8);
        __ pushq(r9);

        __ pushq(rbx); // Callee-save
#endif

        __ Push(Immediate(0)); // Number of successful matches in a global regexp.
        __ Push(Immediate(0)); // Make room for "string start - 1" constant.

        // Check if we have space on the stack for registers.
        Label stack_limit_hit;
        Label stack_ok;

        ExternalReference stack_limit = ExternalReference::address_of_stack_limit(isolate());
        __ movq(rcx, rsp);
        __ Move(kScratchRegister, stack_limit);
        __ subq(rcx, Operand(kScratchRegister, 0));
        // Handle it if the stack pointer is already below the stack limit.
        __ j(below_equal, &stack_limit_hit);
        // Check if there is room for the variable number of registers above
        // the stack limit.
        __ cmpq(rcx, Immediate(num_registers_ * kSystemPointerSize));
        __ j(above_equal, &stack_ok);
        // Exit with OutOfMemory exception. There is not enough space on the stack
        // for our working registers.
        __ Set(rax, EXCEPTION);
        __ jmp(&return_rax);

        __ bind(&stack_limit_hit);
        __ Move(code_object_pointer(), masm_.CodeObject());
        CallCheckStackGuardState(); // Preserves no registers beside rbp and rsp.
        __ testq(rax, rax);
        // If returned value is non-zero, we exit with the returned value as result.
        __ j(not_zero, &return_rax);

        __ bind(&stack_ok);

        // Allocate space on stack for registers.
        __ subq(rsp, Immediate(num_registers_ * kSystemPointerSize));
        // Load string length.
        __ movq(rsi, Operand(rbp, kInputEnd));
        // Load input position.
        __ movq(rdi, Operand(rbp, kInputStart));
        // Set up rdi to be negative offset from string end.
        __ subq(rdi, rsi);
        // Set rax to address of char before start of the string
        // (effectively string position -1).
        __ movq(rbx, Operand(rbp, kStartIndex));
        __ negq(rbx);
        if (mode_ == UC16) {
            __ leaq(rax, Operand(rdi, rbx, times_2, -char_size()));
        } else {
            __ leaq(rax, Operand(rdi, rbx, times_1, -char_size()));
        }
        // Store this value in a local variable, for use when clearing
        // position registers.
        __ movq(Operand(rbp, kStringStartMinusOne), rax);

#if V8_OS_WIN
        // Ensure that we have written to each stack page, in order. Skipping a page
        // on Windows can cause segmentation faults. Assuming page size is 4k.
        const int kPageSize = 4096;
        const int kRegistersPerPage = kPageSize / kSystemPointerSize;
        for (int i = num_saved_registers_ + kRegistersPerPage - 1;
             i < num_registers_;
             i += kRegistersPerPage) {
            __ movq(register_location(i), rax); // One write every page.
        }
#endif // V8_OS_WIN

        // Initialize code object pointer.
        __ Move(code_object_pointer(), masm_.CodeObject());

        Label load_char_start_regexp, start_regexp;
        // Load newline if index is at start, previous character otherwise.
        __ cmpl(Operand(rbp, kStartIndex), Immediate(0));
        __ j(not_equal, &load_char_start_regexp, Label::kNear);
        __ Set(current_character(), '\n');
        __ jmp(&start_regexp, Label::kNear);

        // Global regexp restarts matching here.
        __ bind(&load_char_start_regexp);
        // Load previous char as initial value of current character register.
        LoadCurrentCharacterUnchecked(-1, 1);
        __ bind(&start_regexp);

        // Initialize on-stack registers.
        if (num_saved_registers_ > 0) {
            // Fill saved registers with initial value = start offset - 1
            // Fill in stack push order, to avoid accessing across an unwritten
            // page (a problem on Windows).
            if (num_saved_registers_ > 8) {
                __ Set(rcx, kRegisterZero);
                Label init_loop;
                __ bind(&init_loop);
                __ movq(Operand(rbp, rcx, times_1, 0), rax);
                __ subq(rcx, Immediate(kSystemPointerSize));
                __ cmpq(rcx, Immediate(kRegisterZero - num_saved_registers_ * kSystemPointerSize));
                __ j(greater, &init_loop);
            } else { // Unroll the loop.
                for (int i = 0; i < num_saved_registers_; i++) {
                    __ movq(register_location(i), rax);
                }
            }
        }

        // Initialize backtrack stack pointer.
        __ movq(backtrack_stackpointer(), Operand(rbp, kStackHighEnd));

        __ jmp(&start_label_);

        // Exit code:
        if (success_label_.is_linked()) {
            // Save captures when successful.
            __ bind(&success_label_);
            if (num_saved_registers_ > 0) {
                // copy captures to output
                __ movq(rdx, Operand(rbp, kStartIndex));
                __ movq(rbx, Operand(rbp, kRegisterOutput));
                __ movq(rcx, Operand(rbp, kInputEnd));
                __ subq(rcx, Operand(rbp, kInputStart));
                if (mode_ == UC16) {
                    __ leaq(rcx, Operand(rcx, rdx, times_2, 0));
                } else {
                    __ addq(rcx, rdx);
                }
                for (int i = 0; i < num_saved_registers_; i++) {
                    __ movq(rax, register_location(i));
                    if (i == 0 && global_with_zero_length_check()) {
                        // Keep capture start in rdx for the zero-length check later.
                        __ movq(rdx, rax);
                    }
                    __ addq(rax, rcx); // Convert to index from start, not end.
                    if (mode_ == UC16) {
                        __ sarq(rax, Immediate(1)); // Convert byte index to character index.
                    }
                    __ movl(Operand(rbx, i * kIntSize), rax);
                }
            }

            if (global()) {
                // Restart matching if the regular expression is flagged as global.
                // Increment success counter.
                __ incq(Operand(rbp, kSuccessfulCaptures));
                // Capture results have been stored, so the number of remaining global
                // output registers is reduced by the number of stored captures.
                __ movsxlq(rcx, Operand(rbp, kNumOutputRegisters));
                __ subq(rcx, Immediate(num_saved_registers_));
                // Check whether we have enough room for another set of capture results.
                __ cmpq(rcx, Immediate(num_saved_registers_));
                __ j(less, &exit_label_);

                __ movq(Operand(rbp, kNumOutputRegisters), rcx);
                // Advance the location for output.
                __ addq(Operand(rbp, kRegisterOutput),
                    Immediate(num_saved_registers_ * kIntSize));

                // Prepare rax to initialize registers with its value in the next run.
                __ movq(rax, Operand(rbp, kStringStartMinusOne));

                if (global_with_zero_length_check()) {
                    // Special case for zero-length matches.
                    // rdx: capture start index
                    __ cmpq(rdi, rdx);
                    // Not a zero-length match, restart.
                    __ j(not_equal, &load_char_start_regexp);
                    // rdi (offset from the end) is zero if we already reached the end.
                    __ testq(rdi, rdi);
                    __ j(zero, &exit_label_, Label::kNear);
                    // Advance current position after a zero-length match.
                    Label advance;
                    __ bind(&advance);
                    if (mode_ == UC16) {
                        __ addq(rdi, Immediate(2));
                    } else {
                        __ incq(rdi);
                    }
                    if (global_unicode())
                        CheckNotInSurrogatePair(0, &advance);
                }

                __ jmp(&load_char_start_regexp);
            } else {
                __ movq(rax, Immediate(SUCCESS));
            }
        }

        __ bind(&exit_label_);
        if (global()) {
            // Return the number of successful captures.
            __ movq(rax, Operand(rbp, kSuccessfulCaptures));
        }

        __ bind(&return_rax);
#ifdef _WIN64
        // Restore callee save registers.
        __ leaq(rsp, Operand(rbp, kLastCalleeSaveRegister));
        __ popq(rbx);
        __ popq(rdi);
        __ popq(rsi);
        // Stack now at rbp.
#else
        // Restore callee save register.
        __ movq(rbx, Operand(rbp, kBackup_rbx));
        // Skip rsp to rbp.
        __ movq(rsp, rbp);
#endif
        // Exit function frame, restore previous one.
        __ popq(rbp);
        __ ret(0);

        // Backtrack code (branch target for conditional backtracks).
        if (backtrack_label_.is_linked()) {
            __ bind(&backtrack_label_);
            Backtrack();
        }

        Label exit_with_exception;

        // Preempt-code
        if (check_preempt_label_.is_linked()) {
            SafeCallTarget(&check_preempt_label_);

            __ pushq(backtrack_stackpointer());
            __ pushq(rdi);

            CallCheckStackGuardState();
            __ testq(rax, rax);
            // If returning non-zero, we should end execution with the given
            // result as return value.
            __ j(not_zero, &return_rax);

            // Restore registers.
            __ Move(code_object_pointer(), masm_.CodeObject());
            __ popq(rdi);
            __ popq(backtrack_stackpointer());
            // String might have moved: Reload esi from frame.
            __ movq(rsi, Operand(rbp, kInputEnd));
            SafeReturn();
        }

        // Backtrack stack overflow code.
        if (stack_overflow_label_.is_linked()) {
            SafeCallTarget(&stack_overflow_label_);
            // Reached if the backtrack-stack limit has been hit.

            // Save registers before calling C function
#ifndef _WIN64
            // Callee-save in Microsoft 64-bit ABI, but not in AMD64 ABI.
            __ pushq(rsi);
            __ pushq(rdi);
#endif

            // Call GrowStack(backtrack_stackpointer())
            static const int num_arguments = 3;
            __ PrepareCallCFunction(num_arguments);
#ifdef _WIN64
            // Microsoft passes parameters in rcx, rdx, r8.
            // First argument, backtrack stackpointer, is already in rcx.
            __ leaq(rdx, Operand(rbp, kStackHighEnd)); // Second argument
            __ LoadAddress(r8, ExternalReference::isolate_address(isolate()));
#else
            // AMD64 ABI passes parameters in rdi, rsi, rdx.
            __ movq(rdi, backtrack_stackpointer()); // First argument.
            __ leaq(rsi, Operand(rbp, kStackHighEnd)); // Second argument.
            __ LoadAddress(rdx, ExternalReference::isolate_address(isolate()));
#endif
            ExternalReference grow_stack = ExternalReference::re_grow_stack(isolate());
            __ CallCFunction(grow_stack, num_arguments);
            // If return nullptr, we have failed to grow the stack, and
            // must exit with a stack-overflow exception.
            __ testq(rax, rax);
            __ j(equal, &exit_with_exception);
            // Otherwise use return value as new stack pointer.
            __ movq(backtrack_stackpointer(), rax);
            // Restore saved registers and continue.
            __ Move(code_object_pointer(), masm_.CodeObject());
#ifndef _WIN64
            __ popq(rdi);
            __ popq(rsi);
#endif
            SafeReturn();
        }

        if (exit_with_exception.is_linked()) {
            // If any of the code above needed to exit with an exception.
            __ bind(&exit_with_exception);
            // Exit with Result EXCEPTION(-1) to signal thrown exception.
            __ Set(rax, EXCEPTION);
            __ jmp(&return_rax);
        }

        FixupCodeRelativePositions();

        CodeDesc code_desc;
        Isolate* isolate = this->isolate();
        masm_.GetCode(isolate, &code_desc);
        Handle<Code> code = isolate->factory()->NewCode(code_desc, Code::REGEXP, masm_.CodeObject());
        PROFILE(isolate, RegExpCodeCreateEvent(AbstractCode::cast(*code), *source));
        return Handle<HeapObject>::cast(code);
    }

    void RegExpMacroAssemblerX64::GoTo(Label* to)
    {
        BranchOrBacktrack(no_condition, to);
    }

    void RegExpMacroAssemblerX64::IfRegisterGE(int reg,
        int comparand,
        Label* if_ge)
    {
        __ cmpq(register_location(reg), Immediate(comparand));
        BranchOrBacktrack(greater_equal, if_ge);
    }

    void RegExpMacroAssemblerX64::IfRegisterLT(int reg,
        int comparand,
        Label* if_lt)
    {
        __ cmpq(register_location(reg), Immediate(comparand));
        BranchOrBacktrack(less, if_lt);
    }

    void RegExpMacroAssemblerX64::IfRegisterEqPos(int reg,
        Label* if_eq)
    {
        __ cmpq(rdi, register_location(reg));
        BranchOrBacktrack(equal, if_eq);
    }

    RegExpMacroAssembler::IrregexpImplementation
    RegExpMacroAssemblerX64::Implementation()
    {
        return kX64Implementation;
    }

    void RegExpMacroAssemblerX64::LoadCurrentCharacter(int cp_offset,
        Label* on_end_of_input,
        bool check_bounds,
        int characters)
    {
        DCHECK(cp_offset < (1 << 30)); // Be sane! (And ensure negation works)
        if (check_bounds) {
            if (cp_offset >= 0) {
                CheckPosition(cp_offset + characters - 1, on_end_of_input);
            } else {
                CheckPosition(cp_offset, on_end_of_input);
            }
        }
        LoadCurrentCharacterUnchecked(cp_offset, characters);
    }

    void RegExpMacroAssemblerX64::PopCurrentPosition()
    {
        Pop(rdi);
    }

    void RegExpMacroAssemblerX64::PopRegister(int register_index)
    {
        Pop(rax);
        __ movq(register_location(register_index), rax);
    }

    void RegExpMacroAssemblerX64::PushBacktrack(Label* label)
    {
        Push(label);
        CheckStackLimit();
    }

    void RegExpMacroAssemblerX64::PushCurrentPosition()
    {
        Push(rdi);
    }

    void RegExpMacroAssemblerX64::PushRegister(int register_index,
        StackCheckFlag check_stack_limit)
    {
        __ movq(rax, register_location(register_index));
        Push(rax);
        if (check_stack_limit)
            CheckStackLimit();
    }

    void RegExpMacroAssemblerX64::ReadCurrentPositionFromRegister(int reg)
    {
        __ movq(rdi, register_location(reg));
    }

    void RegExpMacroAssemblerX64::ReadPositionFromRegister(Register dst, int reg)
    {
        __ movq(dst, register_location(reg));
    }

    void RegExpMacroAssemblerX64::ReadStackPointerFromRegister(int reg)
    {
        __ movq(backtrack_stackpointer(), register_location(reg));
        __ addq(backtrack_stackpointer(), Operand(rbp, kStackHighEnd));
    }

    void RegExpMacroAssemblerX64::SetCurrentPositionFromEnd(int by)
    {
        Label after_position;
        __ cmpq(rdi, Immediate(-by * char_size()));
        __ j(greater_equal, &after_position, Label::kNear);
        __ movq(rdi, Immediate(-by * char_size()));
        // On RegExp code entry (where this operation is used), the character before
        // the current position is expected to be already loaded.
        // We have advanced the position, so it's safe to read backwards.
        LoadCurrentCharacterUnchecked(-1, 1);
        __ bind(&after_position);
    }

    void RegExpMacroAssemblerX64::SetRegister(int register_index, int to)
    {
        DCHECK(register_index >= num_saved_registers_); // Reserved for positions!
        __ movq(register_location(register_index), Immediate(to));
    }

    bool RegExpMacroAssemblerX64::Succeed()
    {
        __ jmp(&success_label_);
        return global();
    }

    void RegExpMacroAssemblerX64::WriteCurrentPositionToRegister(int reg,
        int cp_offset)
    {
        if (cp_offset == 0) {
            __ movq(register_location(reg), rdi);
        } else {
            __ leaq(rax, Operand(rdi, cp_offset * char_size()));
            __ movq(register_location(reg), rax);
        }
    }

    void RegExpMacroAssemblerX64::ClearRegisters(int reg_from, int reg_to)
    {
        DCHECK(reg_from <= reg_to);
        __ movq(rax, Operand(rbp, kStringStartMinusOne));
        for (int reg = reg_from; reg <= reg_to; reg++) {
            __ movq(register_location(reg), rax);
        }
    }

    void RegExpMacroAssemblerX64::WriteStackPointerToRegister(int reg)
    {
        __ movq(rax, backtrack_stackpointer());
        __ subq(rax, Operand(rbp, kStackHighEnd));
        __ movq(register_location(reg), rax);
    }

    // Private methods:

    void RegExpMacroAssemblerX64::CallCheckStackGuardState()
    {
        // This function call preserves no register values. Caller should
        // store anything volatile in a C call or overwritten by this function.
        static const int num_arguments = 3;
        __ PrepareCallCFunction(num_arguments);
#ifdef _WIN64
        // Second argument: Code of self. (Do this before overwriting r8).
        __ movq(rdx, code_object_pointer());
        // Third argument: RegExp code frame pointer.
        __ movq(r8, rbp);
        // First argument: Next address on the stack (will be address of
        // return address).
        __ leaq(rcx, Operand(rsp, -kSystemPointerSize));
#else
        // Third argument: RegExp code frame pointer.
        __ movq(rdx, rbp);
        // Second argument: Code of self.
        __ movq(rsi, code_object_pointer());
        // First argument: Next address on the stack (will be address of
        // return address).
        __ leaq(rdi, Operand(rsp, -kSystemPointerSize));
#endif
        ExternalReference stack_check = ExternalReference::re_check_stack_guard_state(isolate());
        __ CallCFunction(stack_check, num_arguments);
    }

    // Helper function for reading a value out of a stack frame.
    template <typename T>
    static T& frame_entry(Address re_frame, int frame_offset)
    {
        return reinterpret_cast<T&>(Memory<int32_t>(re_frame + frame_offset));
    }

    template <typename T>
    static T* frame_entry_address(Address re_frame, int frame_offset)
    {
        return reinterpret_cast<T*>(re_frame + frame_offset);
    }

    int RegExpMacroAssemblerX64::CheckStackGuardState(Address* return_address,
        Address raw_code,
        Address re_frame)
    {
        Code re_code = Code::cast(Object(raw_code));
        return NativeRegExpMacroAssembler::CheckStackGuardState(
            frame_entry<Isolate*>(re_frame, kIsolate),
            frame_entry<int>(re_frame, kStartIndex),
            frame_entry<int>(re_frame, kDirectCall) == 1, return_address, re_code,
            frame_entry_address<Address>(re_frame, kInputString),
            frame_entry_address<const byte*>(re_frame, kInputStart),
            frame_entry_address<const byte*>(re_frame, kInputEnd));
    }

    Operand RegExpMacroAssemblerX64::register_location(int register_index)
    {
        DCHECK(register_index < (1 << 30));
        if (num_registers_ <= register_index) {
            num_registers_ = register_index + 1;
        }
        return Operand(rbp, kRegisterZero - register_index * kSystemPointerSize);
    }

    void RegExpMacroAssemblerX64::CheckPosition(int cp_offset,
        Label* on_outside_input)
    {
        if (cp_offset >= 0) {
            __ cmpl(rdi, Immediate(-cp_offset * char_size()));
            BranchOrBacktrack(greater_equal, on_outside_input);
        } else {
            __ leaq(rax, Operand(rdi, cp_offset * char_size()));
            __ cmpq(rax, Operand(rbp, kStringStartMinusOne));
            BranchOrBacktrack(less_equal, on_outside_input);
        }
    }

    void RegExpMacroAssemblerX64::BranchOrBacktrack(Condition condition,
        Label* to)
    {
        if (condition < 0) { // No condition
            if (to == nullptr) {
                Backtrack();
                return;
            }
            __ jmp(to);
            return;
        }
        if (to == nullptr) {
            __ j(condition, &backtrack_label_);
            return;
        }
        __ j(condition, to);
    }

    void RegExpMacroAssemblerX64::SafeCall(Label* to)
    {
        __ call(to);
    }

    void RegExpMacroAssemblerX64::SafeCallTarget(Label* label)
    {
        __ bind(label);
        __ subq(Operand(rsp, 0), code_object_pointer());
    }

    void RegExpMacroAssemblerX64::SafeReturn()
    {
        __ addq(Operand(rsp, 0), code_object_pointer());
        __ ret(0);
    }

    void RegExpMacroAssemblerX64::Push(Register source)
    {
        DCHECK(source != backtrack_stackpointer());
        // Notice: This updates flags, unlike normal Push.
        __ subq(backtrack_stackpointer(), Immediate(kIntSize));
        __ movl(Operand(backtrack_stackpointer(), 0), source);
    }

    void RegExpMacroAssemblerX64::Push(Immediate value)
    {
        // Notice: This updates flags, unlike normal Push.
        __ subq(backtrack_stackpointer(), Immediate(kIntSize));
        __ movl(Operand(backtrack_stackpointer(), 0), value);
    }

    void RegExpMacroAssemblerX64::FixupCodeRelativePositions()
    {
        for (int position : code_relative_fixup_positions_) {
            // The position succeeds a relative label offset from position.
            // Patch the relative offset to be relative to the Code object pointer
            // instead.
            int patch_position = position - kIntSize;
            int offset = masm_.long_at(patch_position);
            masm_.long_at_put(patch_position,
                offset
                    + position
                    + Code::kHeaderSize
                    - kHeapObjectTag);
        }
        code_relative_fixup_positions_.Rewind(0);
    }

    void RegExpMacroAssemblerX64::Push(Label* backtrack_target)
    {
        __ subq(backtrack_stackpointer(), Immediate(kIntSize));
        __ movl(Operand(backtrack_stackpointer(), 0), backtrack_target);
        MarkPositionForCodeRelativeFixup();
    }

    void RegExpMacroAssemblerX64::Pop(Register target)
    {
        DCHECK(target != backtrack_stackpointer());
        __ movsxlq(target, Operand(backtrack_stackpointer(), 0));
        // Notice: This updates flags, unlike normal Pop.
        __ addq(backtrack_stackpointer(), Immediate(kIntSize));
    }

    void RegExpMacroAssemblerX64::Drop()
    {
        __ addq(backtrack_stackpointer(), Immediate(kIntSize));
    }

    void RegExpMacroAssemblerX64::CheckPreemption()
    {
        // Check for preemption.
        Label no_preempt;
        ExternalReference stack_limit = ExternalReference::address_of_stack_limit(isolate());
        __ load_rax(stack_limit);
        __ cmpq(rsp, rax);
        __ j(above, &no_preempt);

        SafeCall(&check_preempt_label_);

        __ bind(&no_preempt);
    }

    void RegExpMacroAssemblerX64::CheckStackLimit()
    {
        Label no_stack_overflow;
        ExternalReference stack_limit = ExternalReference::address_of_regexp_stack_limit(isolate());
        __ load_rax(stack_limit);
        __ cmpq(backtrack_stackpointer(), rax);
        __ j(above, &no_stack_overflow);

        SafeCall(&stack_overflow_label_);

        __ bind(&no_stack_overflow);
    }

    void RegExpMacroAssemblerX64::LoadCurrentCharacterUnchecked(int cp_offset,
        int characters)
    {
        if (mode_ == LATIN1) {
            if (characters == 4) {
                __ movl(current_character(), Operand(rsi, rdi, times_1, cp_offset));
            } else if (characters == 2) {
                __ movzxwl(current_character(), Operand(rsi, rdi, times_1, cp_offset));
            } else {
                DCHECK_EQ(1, characters);
                __ movzxbl(current_character(), Operand(rsi, rdi, times_1, cp_offset));
            }
        } else {
            DCHECK(mode_ == UC16);
            if (characters == 2) {
                __ movl(current_character(),
                    Operand(rsi, rdi, times_1, cp_offset * sizeof(uc16)));
            } else {
                DCHECK_EQ(1, characters);
                __ movzxwl(current_character(),
                    Operand(rsi, rdi, times_1, cp_offset * sizeof(uc16)));
            }
        }
    }

#undef __

} // namespace internal
} // namespace v8

#endif // V8_TARGET_ARCH_X64
